Electric circuit breaker



Jan. 1, 1946. Q THUMlM ET AL 2,392,201

ELECTRI C C IRCUIT BREAKER Filed Feb. 12, 1941 5 Sheets-Sheet 1 WATERLEVEL Inventors- Car-l Thurnim,

\ David C.Pr-ince,

Herman B.Dhonau,

b Wan/p76. AMMA Then- Attorrwey.

Jan. 1, 1946. c. THuMlM ETAL 2,392,201

ELECTRIC CIRCUIT BREAKER Y Filed Feb. 12, 1941. 3 Sheets-Sheet 2 2 CarlThumim, K David C.F r-ir1ce, Herman E .Dhor1au,

Their" Attorney.

Jan. 4 c. THUMIM ET AL 2,392,201

ELECTRIC C IRCUIT BREAKER Filed Feb. 12, 1941 3 Sheets-Sheet 3 Fig.3.

CIA/76R Fig.4.

Inventors:

Carl Thurnim, David Cfl rflnce, Herman-1 E .Dhonau.

" Their- Attorney.

Patented Jan. 1, 1946.

ELECTRIC CIRCUIT BREAKER Carl Thumim, Yeadon, Pa., David C. Prince, QSchenectady, N. Y., and Herman B. Dhonan, Philadelphia, Pa., assignorsto General Electric Company, a corporation of New York ApplicationFebruary 12, 1941, Serial No. 378,536

12 Claims.

Our invention relates to electric circuit breakers for interrupting highvoltage power circuits, more particularly to circuit breakers havingdisconnecting means for electrically disconnecting or isolating themovable contacts of the breaker with respect to the power circui and hasfor its principal object the provision of an improved circuit breaker ofthe aforesaid type having disconnecting means for automatically formingan isolating gap in series with the breaker after interruption of thepower circuit and for closing the circuit at said gap only after closingof the main breaker interrupting contacts so that the circuit is notmade at said interrupting contacts.

The conventional oil circuit breaker operates by both making andbreaking the main power circuit at the interrupting contacts. The goodare extinguishing and insulating characteristics of the oil practicallyeliminate arcing during the making operation and so serve to protect thecontacts from excessive deterioration. Also, since the oil has highdielectric strength, the contacts may remain immersed in the oil aftercircuit interruption without danger of voltage breakdown due to leakagecurrents. However, when an arc extinguishing liquid having comparatively-low dielectric strength, such as water for example, is used in place ofoil the circuit making operation is frequently accompanied by excessiveleakage current and arcing and failure of the breaker to close. That is,the high explosivelike pressures generated by power currents or arcingwithin the extinguishing liquid that may occur prior to actualengagement of the contacts tend to force the breaker open again therebymaking the closing operation difficult, if not impossible. Obviously,the arcing in such cases may also be destructive to the interruptingcontacts,

Also, the opening operation must be followed immediately b a separateisolating or disconnecting operation in order to prevent voltagebreakdown within the interrupting chamber and reestablishment of arcing,

In accordance with our invention, these disadvantages are overcome byproviding means for opening and disconnecting the breaker so as toprevent fiashover or failure after actual interruption, i. e., first, bybreaking the circuit at the interrupting contacts and then opening thedisconnecting contacts, preferably in air, and, for eliminating in theclosing operation arc chamber pressures, first, by closing theinterrupting contacts in the arc extinguishing liquid while the circuitis still open at the disconnecting contacts, and finally closing,preferably with a high speed snap action, the disconnecting contacts tocomplete the power circuit. By means of this arrangement, we eliminateall the prior difl'iculties at the interrupting contacts whilesuccessfully closing with minimum deterioration the disconnectingcontacts to complete the power circuit.

Our invention will be more fully setforth in the following descriptionreferring to the accompanying drawings, and the features of noveltywhich characterize our invention will be pointed out with particularityin the claims annexed to and forming a part of this specification.

Referring to the drawings, Fig, 1 is an elevational view, partly insection of a double-break circuit breaker embodying the presentinvention in a partially open circuit position prior to the closingthereof, Fig. 2 is a plan view taken along the line 2-2 of Fig. 1, Fig.3 is an enlarged view of a part of the circuit breaker shown by Fig. 1,Fig. 4 is a view similar to Fig. 3 showing the mechanism and breaker in'the closed circuit position, and Fig. 5 is an elevational side view ofthe breaker shown in Fig. 1.

Referring to Fig. 1, there is illustrated by way of example a watercircuit breaker having two interrupting breaks in series arrangedrespectively, in the interrupting chambers l and 2. The interruptingchambers contain water as the arc extinguishing liquid and suitablebaflie structure (not shown) for insuring rapid interruption of thecircuit b the well-known "cross-blast"- action. It shall be understoodof course that any other liquid having suitable arc extinguishingcharacteristics can be used without departing from the spirit of ourinvention, and that the term "water as used herein is intended toinclude any are extinguishing liquid having such dielectric propertiesthat an additional isolating or disconnecting break in series externallyof the interrupting chamber is required for the purpose of preventingleakage current and arcing within the interrupting chamber subsequent toactual breaking of the circuit and prior to actual making of thecircuit.

The interrupting chambers i and 2 are preferably liquid tight so thatthere is no loss of liquid during an opening operation, Each chambercomprises a steel cylinder suitably lined with insulating material andclosed at the upper and lower ends by members 3 and 4 which clampbetween them the steel cylinder by means of tie rods 5. The steelinterrupting chambers are supported on insulating bushings 6 and areconnected to terminal plates 1 of the main power circuit. The steelcylinders also connect with the fixed interrupting contact structures 8and 9 within the interrupting chambers respectively.

The movable interrupting contacts for coacting with the fixed contacts 8and 9 comprise conducting rods l8 and l l guided through the tops of theinterrupting chambers by insulating bushings l2 and I3 respectively, andrigidly secured in a manner hereinafter described to an insulatingcrosshead l4. A lift rod i5 is secured to the crosshead M for operatingit in vertical rectilinear motion for opening and closing the circuitbreaker.

For the purpose of electrically connecting and disconnecting the contactrods It and II with respect to each otherin accordance with the presentinvention, a bridging member It is car- I6 is supported in dependingrelation from the crossbar It by a T-shaped metal casting I? that isrigidly secured as indicated at I8 to the crossbar and the lift oroperating rod I5. Means,

hereinafter described, are provided for locking the bridging member itso as electrically to connect the contact rods 80 and II when thebreaker is closed and also during all but the final part of the openingoperation, and for locking the bridging member in disconnecting positionwith respect to the contact rods in the fully open circuit position andalso during the closing operation except for the final part thereof.

The insulating crossbar it and the bridging structure or blade I6 can beconsidered as a single assembly operable by the liftrod I and associatedmeans. As will be noted by reference to Fig. 2, the crossbar Itcomprises a pair of spaced insulating rods which are composed ofmechanically strong insulating material, such as laminated wood. Thebridging blade I6 is also composed of a pair of spaced blade-likeconductors, each blade being in turn composed of two closely spacedparallel sections as illustrated. The blade structure is united by abracket I 6' as best illustrated by Fig. 5. This arrangement providesfor compactness since the crossbar can nest within the bridging bladewhen the two are locked together in the contact-connecting position.

The crossbar it has secured at each end between the wood bars thereof anelongated metalmovable interrupting contact rods In and II respectivelyare mounted and secured. The outer end portions of each member I9 areformed as socket contacts for receiving coacting plug contacts 22 (Figs.2 and 3) carried by the bridging blade It. The plug contacts 22 aremounted directly beneath the socket contacts '2! on the bridge I6 at theends of each double-blade. As shown at the right side of Fig. 2, theplug contacts 22 are clamped as at 23 between the laminatedblade,sections at each side of the bridging blade proper.

As shown, there are four sets of the disconnecting or tertiary contacts2! and 22, although it will be apparent that two sets of such contactsare suflicient for the purposes of the present invention'. Whenthecontacts 2| and 22 are in engagement as shown by Fig. 4, there will be acontinuous electrical circuit between the interrupting contacts In andII by way of the conducting supports I9, socket contacts 2|, plugcontacts 22, and the conducting-bridge or blade structure IS.

The bridging blade I6 is guided for limited vertical reciprocal movementwith respect to the crossbar It by means of a pair of rollers 24'secured to opposite inner sides of the bridging blade movable withincoacting vertical guides 25 formed in the supporting casting I'I(Figs.'2 and 3). Also for the purpose of guiding the bridging blade andalso the assembly for vertical rectilinear movement, the bridging blade.I6 is provided withrollers 26 secured to the depending bracket It forcentering the complete bridging assembly between the cams 21 that aremounted on the interrupting chambers I and 2 respectively. Thisarrangement is clearly shown by Figs. 3 and 4, Fig. 4 illustrating therollers coacting with the inner'lateral cam surfaces when the breaker isclosed.

In order to lock and unlock for relative movement the bridging blade ISwith respect to the crossbar It, a pair of similarly arranged togglessymmetrically disposed near the opposite ends of the bridging bladeinterconnect the bridging blade and the casting support Ii. As moreclearly shown in Fig. 3, each toggle comprises a link 28 pivotallyconnected at 29 to the support i1, and a link 80 pivotally connected at3! to the bridging blade I6. The two links of the toggle are connectedat 32 to form the knee joint and a .roller 33 is copivotally mountedon'the toggle knee joint. The link 30 is provided with a cam surface 38'for a purpose hereinafter described.

A toggle locking spring 85 interconnects the blade It and a flange 36"on the link 30.

In the disconnected position shown by Fig. 3, it will be noted(referring to the toggle centers 3|, 29 and 32) that thetoggle is heldby the spring 3 8 in an overset locking position so that the support I1and the blade are locked together as a unit. That is, the toggle knee 32is past. the toggle center line defined by the pivots 29 and 3'! asclearly shown'by the drawings. In order for the blade to be unlockedwith respect to the crossbar I4, it is first necessary to cause collapseof the toggle by moving the toggle knee 32 in clockwise direction untilit crosses the toggle; center line. The toggle will then be free tocol-x, lapse to its stretched-out position shown by Fig. 4.

Let it now be assumed that the circuit breaker is in the closed circuitconnected position indicated by Fig. 4. In this position, theinterrupting contacts 8-lt and 9-H (Fig. 1) are in engagement within theinterrupting chambers and the, circuit is completed between theinterrupting con-' tacts by the bridging blade I6 and the coactingdisconnecting contacts 2I and 22. Also a current path shunting thedisconnecting contacts for carrying continuous load currents in theclosed position of the breaker is formed by the bridging blade. I6 andprimary contacts 35 which are mounted on top of each interruptingchamber on terminals '3 directly beneath coacting contact portions 36formed at the opposite ends of the blade. The primary contacts areelectrically conv nected to the steel interrupting chambers which are inturn directly connected to the terminal conductors l and carry the loadcurrent directly through the breaker shunting both the interrupting, orsecondary contacts and the disconnecting, or tertiary contacts. Theprimary contacts are subjected to no arcing whatever and open first,thereby shunting the current to the interrupting contacts and closeafter both the interrupting and disconnecting contacts have madeengagement for establishing the'powercircuit.

In the closed circuit position (Fig. 4), it is essential that thetoggles not only be locked but beheld in locked position for maintainingthe disconnecting contacts in engagement until the circuit has beeninterrupted by the secondary contacts. In this position, each toggleroller 32 is held by the corresponding cam 21 in an overset positionwith respect to the toggle center line indicated so that the blade andcrosshead are locked together in the extended position of the toggle.

Let it now be assumed that the breaker is to be tripped bpen in responseto a fault or overload in the conventional manner. This actuatesmechanism (not shown) for raising the lift rod l5. When the lift rod israised to open the breaker the entire bridging assembly M-lli, includingthe interrupting rod contacts In and H moves upward as a unit. Theprimary contacts 35-35 first separate shunting the current through theinterrupting contacts and when in turn the interrupting contactsseparate the arc is extinguished within the interrupting chambers bysuitable arc extinguishing baflies forming no part of the presentinvention. The disconnecting contacts 2 |-22 are still locked togetherduring this partof the opening operation of the breaker.

After the rod contacts l and H have been raised suiiiciently to clearthe circuit, it is safe to open the disconnecting contacts in seriestherewith so as to form isolating gaps in air exteriorly of theinterrupting chambers. For this purpose, there is provided, referring toFigs. 1 and 4, a pair of toggle actuating members 31. each of which ispivotally mounted at 38 on the fixed overhead guide structure 39 andprovided at its outer end with a roller 40. Guiding and spring buffermeans indicated at 4| are connected to each of the pivoted members 31and coact with stationary insulating structure 42 forming a part of thefixed structure 39. The members 31 are spring biased downward asillustrated and are positioned so that the rollers 40 are directly abovethe top edges of opposite portions of the bridging blade l6.Accordingly, when the blade 68 reaches the rollers 49 near the end ofthe opening stroke, the members 37 are rotated upwardly and the rollers4!] slide laterally in outward directions along the top edges of theblade. The cam portions 30' of the toggle links 30 are so positionedwith respect to the rollers 40 that this sidewise camming of the rollerscauses them to engage the cam surfaces 30! and rotate the toggle links30 so as to trip the toggles. That is, the toggle knee in each case ismoved over the toggle center line indicated in Fig. 4 so that the toggleis free to buckle. This action is clearly indicated in dotted lines atthe upper part of Fig. 4 wherein the toggle link 36 is indicated afterhaving been rotated clockwise approximately 45.

As the toggles 28-35) collapse under the weight of the bridging bladeassembly and the force exerted by spring ll acting through roller 40against the upper edge of bridging blade it, the disconnecting contacts2i-22 separate and assurne a disconnected position shown by Fig. 3. Thetoggle springs 34 continue to buckle the toggles until the knee joint isthrown over the center line again to lock the toggles. The breaker isnow completely open and a pair of isolating gaps in air are in serieswith the open interrupting contacts in the chambers l and 2. There istherefore no danger of flashover within the interrupt ing chambers dueto leakage current through the water or moisture on the chamber walls.

Let it now be assumed that the breaker is to be closed. When the liftrod I5 is lowered to initiate the closing operation, the entire bridgingassembly, together with the rod contacts i0 and H moves downward. Atthis time, the disconnecting contacts 2l-22 are locked by the toggles inthe disconnected position illustrated by Fig. 3. when the assembly nearsthe end of the closing stroke, the interrupting contacts 8-! D and 9-| Iengage but no arcing is encountered within the interrupting chambers dueto the fact that the disconnecting contacts 21-22 are still locked open.When, however, the blade l6 reaches a position where the toggle rollers33 engage the cams 27, further downward movement of the lift rod l5causes the rollers 33 to be cammed upwardly (in a clockwise direction inFig. 3) so that the toggle knees 32 move over the toggle center linesand the toggles unlock. The continued downward movement of the lift rodrotates the toggle roller so as to throw the bridging blade upwardly.The configuration of the cam surface 21 coacting with toggle linkage25-30 is such that there is an upward motion of bridging blade I6 whilethe toggle pin 29 and therefore the contacts 21 are moving downward.Therefore, the velocity of approach of contacts 2| and 22 is the sum oftheir individual velocities. This is greater than the velocity of I5downward and results in a snap action. It will be noted that when thetoggles collapse, each roller 33 rotates approximately (clockwise inFig. 3) so as to move to the outer side of and be held by the cam 2! inoverset locking position in the closed position of the breaker.

The power circuit is therefore made in air at the disconnecting contacts2| -22, thereby eliminating any arcing difficulties within theinterruptin chambers during the closing operation. The rapid andpositive manner in which the power circuit is made substantiallyprecludes material burning of the contacts, and we have found that theclosing operation is not only greatly facilitated but is veryeificiently performed with this arrangement.

At the final part of the stroke, the primary contacts 35-36 engage forthe purpose of providing, in the manner previously "described, a shuntpath for carrying the continuous power current. The breaker is now inthe completely closed position shown by Fig. 4 wherein the disconnectingcontacts are locked closed and the breaker is in readiness for anotheropening operation as previously described.

It should be understood that our invention is not, limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of our invention.

What we claim as new and desire to secure by Letters Patent is:

1. An electric circuit breaker comprising an arc extinguishing chambercontaining a liquid havin a dielectric strength less than oil, fixed andmovable interrupting contacts separable within said liquid forextinguishing arcing, actuating means connected to said-movable contactfor forming an interrupting gap within said chamher, a disconnectingcontact also movable with said actuating means and electricallyconnected to said movable interrupting contact, a coaoting disconnectingcontact mounted for limited movement on said actuating means betweenconnecting and disconnecting positions with respect to said first-nameddisconnecting contact, locking means interconnectin said actuatig meansand coacting disconnecting contact for locking the disconnectingcontacts in connecting position during the arc extinguishing operationwhen the breaker is opened, means for causing unlocking and opening ofsaid disconnecting contacts when the breaker is completely open to forma disconnecting gap in series with said interrupting gap, said lockingmeans also locking said disconnectin contacts in disconnecting positionin the open circuit position of the breaker and during the closingstroke thereof until said interrupting contacts have closed, and meansfor thereupon causing unlocking of said disconnecting contacts so as tomake the power circuit at said disconnecting contacts.

2. An electric circuit breaker comprising an arc extinguishing chambercontaining a liquid having a dielectric strength less than oil, fixedtuating means connected to said movable contact for forming aninterrupting gap within said chamber, a disconnecting contact alsomovable with said actuating means and electrically connected to saidmovable interrupting contact, a coacting disconnecting contact mountedfor limited reciprocal movement on said actuating means betweenconnecting and disconnecting positions with respect to said first-nameddisconnecting contact, locking mean including a toggle interconnectingsaid actuating means and coacting disconnecting contact for locking thedisconnectin contacts together in connecting position during the arcextinguishing operation when the breaker is opened, means for causingbuckling and unlocking of said toggle and opening or said disconnectingcontacts when the breaker is completely open to form a disconnecting gapin series with said interrupting gap, said locking t gle means alsomovable to another position for locking said disconnectin contacts indisconnecting position in the open circuit position of the breaker andduring the closing stroke thereof until said interrupting contacts haveclosed, and means for thereupon causing buckling and unlocking of saidtoggle and closing of said disconnecting contacts so as to make thepower circuit at said disconnecting contacts.

3. An electric circuit breaker comprising an arc extinguishing chambercontaining a liquid having less dielectric strength than oil, fixed andmovable interruptin contacts separable within said liquid forextinguishing arcing, actuating means connected to said movable contactfor forming an interrupting gap within said chamber,

a disconnecting contact also mounted on said actuating means andelectrically connected to said movable interrupting contact, a coactingdisconnecting contact slidably mounted for limited reciprocal movementon said actuating means between conneoting and disconnecting positionswith respect to said first-named disconnecting contact, a locking toggleinterconnecting said actuating means and coacting disconnecting contactarranged to be overset for locking the disconnecting contacts togetherin connecting position during the arc extinguishing operation when.

the breaker is opened, cam means for causing buckling and unlocking ofsaid toggle and openin of said disconnecting contacts when the breakeris completely open to form a disconnecting gap in series with saidinterrupting gap, said toggle also movable through its buckled positionto another overset position for locking said disconnecting contacts indisconnecting position in the open circuit position of the breaker andduring the closing stroke thereof until said interrupting contacts haveclosed, and additional cam means for thereupon causingbuckling andunlocking of said toggle for closin said disconnecting contactssubstantially at the end of the breaker closing stroke so as to make thepower circuit at said disconnecting contacts. I

4. An electric circuit breaker comprising an arc extinguishing chambercontaining a liquid having less dielectric strength than oil, fixed andmov- 'and movable interrupting contacts separable within said liquidiorextinguishing arcing, ac-

able interrupting contacts separable within said liquid forextinguishing arcing, actuating means connected to said movable contactfor forming an interrupting gap within said chamber, a disconnectingcontact also mounted on and movabl with said actuating means andelectrically connected to said movable interrupting contact, a coactingdisconnecting contact mounted for limited reciprocal movement on saidactuating means between connecting and disconnecting positions withrespect to said first-named disconnecting contact, a locking toggleconnected at its opposite ends tosaid actuating means and coactingdisconnecting contact respectively for locking the disconnectingcontacts together in connecting position during the arc extinguishingapart in disconnecting position in the open circuit position of the:breaker and during the closing stroke thereof until said interruptingcontacts have closed, and additional cam means for thereupon causingbuckling and unlocking of said toggle, said additional cam means and theaforesaid spring means coacting to move said toggle in snap-action tothe first-named locking position for closing at high speed saiddisconnecting contacts so as to make the power circuit at saiddisconnecting contacts.

5. An electric circuit breaker of the multiple chambers, an arcextinguishing liquid within said' chambers, interrupting contactsseparable within said liquid in each of said chambers to form in!terrupting gaps, actuating means for separating said contacts,disconnecting contacts arranged to coact with said interrupting contactsexteriorly of said chambers to form two gaps in series relation to saidinterrupting gaps, means for mounting said disconnecting contacts onsaid actuating means so as tomove as a unit therewith for a part of itsmotion but with a lost-motion relation to said actuating means so as toprovide for sequential openingand closing of said interrupting anddisconnecting conta'cts,-means for locking said disconnecting contactsin connecting relation to said interrupting contacts in the closedcircuit position of the breaker and during the arc extinguishingoperation, and for locking said disconnecting contacts in disconnectingposition with relation to said in errupting contacts in the open circuitposition of the breaker and during the closing stroke until afterengagement of said interrupting contacts, and means for unlocking saiddisconnecting contacts whereby the power circuit is made at saiddisconnecting contacts.

. 6. An electric circuit breaker or the multiple break type comprising apair of arc extinguishing chambers, an arc extinguishingliquid withinsaid chambers, interrupting contacts separable within said liquid ineach of said chambers to form interrupting gaps, actuating means forseparating said contacts, disconnecting means including a bridging bladearranged to interconnect said interrupting contacts exteriorly of saidchambers and also to form two gaps in series relation to saidinterrupting gaps, means for mounting said bridging blade on saidactuating 'means in lost motion-relation thereto for the connecting anddisconnecting operations thereof, means for locking said blade inconnecting relation to said interrupting contacts in the closed circuitposition of the breaker and during the arc extinguishing operation, andfor locking said blade in disconnecting position with relation to saidinterrupting contacts in the open circuit position of the breaker andduring the closing stroke until after engagement of said interruptingcontacts, and means operable in accordance with the position'of saidactuating means for unlocking said blade at the end of said closingstroke whereby the power circuit is made at said disconnectin means, andfor unlocking said blade at the end of said opening stroke.

'7. An electric circuit breaker of the multiple .break type comprising apair of arc extinguishing chambers, an arc extinguishing liquid withinsaid chambers, fixed and movable interrupting contacts separable withinsaid liquid in each of said chambers to form interrupting gaps,actuating means connected to said movable contacts, disconnectingcontaots also carried by said actuating means and electrically connectedto said interrupting contacts, a bridging conducting blade carryingdisconnecting contacts arranged to coact with the aforesaiddisconnecting contacts exteriorly of said chambers to form twodisconnectin gaps in series relation'to said interrupting gaps, meansfor mounting said bridging blade on and in lost motion relation to saidactuating means providing for moving between connected and disconnectedpositions with respect to said firstnamed' disconnecting contacts, andmeans for locking said blade in connecting relation in the closedcircuit position of said interrupting contacts and during the arcextinguishing operation, and for locking said blade in disconnectingposition in the open circuit position of said interrupting contacts andduring the closing stroke thereof until after engagement of saidinterrupting contacts, and means for unlocking said disconnectingcontacts to form said disconnecting gaps after the power circuit hasbeen broken and for making the power circuit at said disconnectingcontacts.

8. An electric circuit breaker comprising an arc extinguishing chambercontaining water, interrupting contacts separable within said water forextinguishing arcing, actuating means for separatingsaid contacts toform an interrupting gap entirely within said chamber, disconnectingcontacts disposed exteriorly of said chamber arranged to form anadditional isolating ap in air in series with said interrupting watergap,

, means for mounting said disconnecting contacts on said actuating meansapart from said interrupting contacts so that said disconnectingcontacts move as a unit with said actuating means for a portion of itsoperation, spring and toggle means associated with said actuating meansand said disconnecting contacts arranged to cause opening of saiddisconnecting contacts near the end of the opening operation of saidinterrupting contacts, said spring and toggle means also in the initialclosing operation holding said disconnecting contacts for first causingclosing of said interrupting contacts Within said chamber andsubsequently causing closing of said disconnecting contacts with snapaction at a much higher speed than said interrupting contacts tocomplete the power circuit at Su disconnecting contacts.

9. An electric circuit breaker comprising an are extinguishing chambercontaining a liquid having comparatively low dielectric strength,interrupting contacts separable within said liquid for extinguishingarcing, actuating means comprising :3 a movable operating rod forseparating said contacts to form an interrupting gap entirely withinsaid chamber, disconnecting contacts disposed exteriorly of said chamberarranged to form an additional isolating gap in series with saidinterrupting gap, means for mounting said disconnecting contacts on saidoperating rod so as to move as a unit therewith for a predeterminedportion of its motion, locking means interconnecting said interruptingand disconnecting contacts, and means coacting with said locking meansfor causign separation of said disconnecting contacts subsequent toseparation of said interrupting contacts, said locking means thereuponholding said interrupting contacts open during closing of saidinterrupting contacts within said chamber to provide for closing of thepower circuit at said disconnecting contacts.

10. An electric circuit breaker of the multiple break type comprising apair of arc interrupting contacts, a movable operating rod connected toone of said contacts for causing relative movement of said interruptingcontacts in response to movement of said operating rod, a pair ofdisconnecting contacts serially arranged with said interruptingcontacts, eachor said disconnecting contacts being mounted so as to movewith said operating rod for a portion of the motion thereof whileremaining fixed relative to the other disconnecting contact, and meansresponsive to a predetermined movement of said operating rod in onedirection for causing relative movement of said disconnecting contacts.

11. An electric circuit breaker oi the multiple break type comprising apair of arc interrupting contacts, a movable operating rod connected toone of said contacts for causing relative separation of saidinterrupting contacts in response to movement in one direction of saidoperating rod, a pair of disconnecting contacts serially arranged 45with said interrupting contacts, each of said disconnecting contactsbeing mounted so as to move with said operating rod in said onedirection for a portion of the motion thereof while remaining fixedrelative to the other disconnecting contact, 60 and means responsive toa predetermined movement of said operating rod in a direction toseparate said interrupting contacts for causing relative separation ofsaid disconnecting contacts following separation of said interruptingcontacts.

12. An electric circuit breaker of the multiple break type comprising apair of arc interrupting contacts, a movable operating rod connected toone of said contacts for causing closing of said interrupting contactsin response to movemet in one direction of said operating rod, a pair ofdisconnecting contacts serially arranged with said interruptingcontacts, each of said disconnecting contacts being mounted so as tomove with said operating rod in said one direction for a portion of themotion thereof while remaining fixed relative to the other disconnectingcontact, and means-responsive to a predetermined movement of saidoperating rod in a direction to close said interrupting contacts forcausing closing of said 0 disconnecting contacts following closing ofsaid interrupting contacts.

CARL THUMIM. DAVID C. PRINCE. HERMAN B. DHONAU.

